Wordpress - Is there a has_more_tag() method or equivalent?

Making a quick note of the codes we could use to show the_content(); if the More tag exists, and the_excerpt(); if it doesn't.

Code #1 (Recommended)

<?php
    if( strpos( $post->post_content, '<!--more-->' ) ) {
        the_content();
    }
    else {
        the_excerpt();
    }
?>

(Credit: MichaelH)

Code #2

<?php
    if( strpos( get_the_content(), 'more-link' ) === false ) {
        the_excerpt();
    }
    else {
        the_content();
    }
?>

(Credit: Michael) Basically does #1 the other way around.

Code #3

<?php
    if( preg_match( '/<!--more(.*?)?-->/', $post->post_content ) ) {
        the_content();
    }
    else {
        the_excerpt();
    }
?>

(Credit: helgatheviking) For use only in edge cases where you cannot use strpos(). Generally strpos() is more efficient than preg_match().

---

Making it more conditional:

<?php
    if ( is_home() || is_archive() || is_search() ) {
        if( strpos( $post->post_content, '<!--more-->' ) ) {
            the_content( __( 'Continue reading <span class="meta-nav">&rarr;</span>', 'twentytwelve' ) );
        }
        else {
            the_excerpt();
        }
    }
    else {
        the_content();
    }
?>

What does it do? If the page shown is home, archive or search results page, then show the_content(); if the More tag exists, the_excerpt(); if it doesn't, and simply show the_excerpt(); on all other pages.

Quite simply put: there is no built in function that does the same thing as your code above.

Bonus content: More tag tricks